Conventional power strapping machines for strapping packages use a strapping device in tandem with a compression device. Typical prior art designs present many problems which vastly affect cost and efficiency. The present invention is intended to overcome these problems.
Many prior art strapping devices use a single coil of strapping that is connected to a guide track. The guide track is connected to a chute that is used for routing the strapping around a package. The strapping is then stripped out of the chute. The guide track has an accumulator box included in the design for storing extra strapping that is fed into the machine while the package is being strapped and for storing strapping that is taken up while the strapping is being tightened.
The usage of single coil of strapping presents a fundamental problem in itself. When the coil is out of strapping, the operator must manually reload a new coil of strapping. To do this, the machine must be taken off line, thereby wasting valuable production time. Several other problems arise in the prior art. The use of a single accumulator box for storing extra strapping that is fed in during the strapping process and for storing strapping that is taken up when the strapping is tensioned around a package can cause tangles in the strap in the box. The strap that is brought in from the tensioning and the extra strapping being fed in, tend to rub against each other and tangle. When a tangle occurs, the operator must stop production and manually untangle the strapping.
Prior art designs have also had problems with devices that sense whether the accumulator box is too full to accept more strapping. Some designs use mechanical switches that are operated by the physical strength of the strapping. This design, however, is not reliable, since it varies with the different operating conditions present, such as, for example, temperature, humidity, and the force required to operate the mechanical switch. Other prior art designs use a photo electric eye and reflector system. This design is not reliable, however, because dust and contaminants can interfere with the system.
Another problem in typical prior art designs is the usage of a chute that must have the strapping stripped out in order to tension the strap around the package. Stripping can cause nicks in the chute which shortens the life of the chute and can cause short feeds and pre-sealing to occur.
Prior art compression devices also present many problems. The typical prior art compression device uses a single solid bar to compress the package so that the strapping device can tension the strap tightly around the package.
This solid bar, by itself, presents a safety hazard. Often, if the operators need to place their hands in the compression path for any reason, the hands will be crushed by the solid bar.
Also, the use of a single compression device on one side of the package centerline causes the strap to be placed on the package in a butterfly configuration. The butterfly configuration can contribute to the strap becoming loose during transit.
The present invention is intended to overcome or minimize all of these problems, as well as to present several other improvements.